Solved BSODs. May be helps someone.
Since installing Windows 7 x64 last moth had a lot of problems (pc has 4GB
memory). Random BSOD in the drivers
and ntoskrnl, the usual software crashes. Changing of graphics card and sound cards didn't help, removing and reinstalling applications too. Memtest86 ran with zero errors for many tries.
The problem was solved by simple CMOS clearing (jumper). After that BIOS detected the memory as DDR333 instead of DDR400 (though it is DDR400). Additionally, I switched off Software Memory Remapping, leaving only the hardware one (otherwise, Windows sees only 3GB) - have both, don't know why.
Since than Windows works absolutely stable. No more crashes in FF, IE. No more BSODs.
Conclusion: even memtest86+ could run well, try to change memory or reduce the speed. Of course, it's valid for the case, when BSODs are really random...